A Simple and Reliable Method of Endotracheal Intubation in Mice: Advantages of Exposing the Trachea

Mice are popular models in experimental studies because they can be genetically modified and have a short  gestation period. In long-term studies requiring recovery from anesthesia or repeated measurements of pulmonary  function, endotracheal intubation is advantageous. However, this is difficult because of the small  anatomic structures involved. Various methods have been previously reported, the majority of them calling  for expensive devices or techniques which require special training. Therefore, we have created a simple  method of endotracheal intubation in mice using a light-emitting diode (LED) light, a metal laryngoscope,  a 22-gauge plastic cannula and a stylet made of a 0.3mm piano wire, which can all be easily prepared.  Transillumination after exposure of the trachea makes it possible to illuminate the oropharynx with a lowpriced  LED light and a metal laryngoscope provides good visualization of the tracheal opening. With direct  vision, a 22-gauge plastic cannula can easily be inserted into the trachea. The custom-made stylet is suitably  flexible for performing tracheal intubation without tissue injury. In a series of 42 mice, the success rate with  the procedure was 97.6% (n=41). Only in one case was it necessary for the procedure to be repeated. There  were no airway complications. Though exposure of the trachea is invasive, it does have advantages. We  conclude that this method is simple, safe and inexpensive, and could be used by any researchers interested  in it, no matter how small their budget.

Modeling Credit Risk: A Structural Approach with Long-term and Short-term Debts

This paper proposes a structural model to price credit risk of firms with short-term and long-term debts. This enables one to distinguish between default probabilities in the short run and in the long run, and to identify how the composition of debts affects credit risk. We endogenize the banks' decision to bankrupt or save firms in insolvency, and analyze the influence of the governance structure on credit risk valuation.